Telephone-circuit.



No. 683,505. Patented out. |901.

c. E. scmusn. TELEPHONE CIRCUIT.

(Application l'ed Ian. 20, 1900.)

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PATENT CHARLES E. SCRINER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERN ELECTRIC COMPANY, OE SAME PLACE.

TELEPHONE-CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 683,505, dated October 1, 1901.

Application led January 20, 1900. Serial No. 2,108. (No model.)

T a/ZZ whom, it may concern:

Beit known that I, CHARLES E. SGRIBNER, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone- Circuits, (Case No. 482,) of which the following is a full, clear, concise, and exact description.

This invention concerns the prevention of the propagation of alternating or pulsating currents through continuous conductors, its object being to permit the junction of different circuits conveying such currents While maintaining the independence of the circuits with respect to the alternating or pulsating currents, or, so to speak, localizing the variations of the currents in the respective circuits. It is addressed particularly to telephone-circuits which are united for the trans- 'mission of signals or for the supply of current for exciting-transmitters, but of which the independence from one another must be maintained to prevent cross-talk.

In a patent, No. 559,410, granted to C. E. Scribner and F. R. McBerty May 5, 1896, I have, jointly with F. R. McBerty, disclosed a mode of localizing the fluctuations of current in a conductor by means of a distributed impedance in the conductors uniting the circuits wherein the fluctuations are to be localized, and shunts or bridges between the two conductors unite the dierent circuits intermediate oi' the impedance-coils, which prevents the transmission of alternating or pulsating currents from one of the circuits into the other through the conductors so provided with the distributed impedance and return circuits.

The present invention is an extension of and improvement over the patented invention, whereby the waste of current through the return shunts or bridges is prevented without loss of efficiency in localizing the varying currents; and it consists in the provision of condensers in place of resistance-coils in the shunts or return paths. In other words, the present invention involves conductors uniting what may be considered as a source of current with a circuit, distributed large impedance in the conductors, and large capacity between the two conductors also distributed or segregated at intervals throughout the impedance.

I have made application of this invention to telephone-lines over which current is supplied from a central point .to a secondary center and therefrom to telephone-lines radiating from the secondary center for exciting the transmitting-telephones of any lines in pairs or singly, while permitting the inde- 6o pendent use of the main circuit and of the subcircuits simultaneously for telephonie transmission. This is accomplished by leading the so-called subcircuits or extensioncircuits from the terminals of the main cir- 55 cuit or source of supply through conductors containing considerable impedance distributed at intervals throughout their length and providing bridges of the supply-circuit between the conductors thereof containing con- 7c densers.

The particular application of the invention mentioned is illustrated diagrammatically in the attached drawing. Therein I have shown a main telephone-line, which may be considered as extending through a telephone central station or other point at which the source of current-supply is located and at one terminal to a secondary center, from which several extension telephone-lines radiate.

Referring to the drawing, the main or common source of current ais connected with the line-conductors 1 2 and 3 4, respectively, of two telephone-lines, which may, in fact, be regarded as a single telephone-circuit, the circuit being inductively complete through windings of a repeating-coil b. The linewires 1 and 2 lead to a telephone-substation C, where they are united through a transmitting and a receiving telephone. The line- 9o wires 3 and 4 lead to another station D, which is not onlya telephone-substation, but which also forms the center from which radiate other extension telephone-lines 5 6, 7 8, and 9 10 to substations E, F, and G, respectively. Each 9 5 of these stations D, E, F, and G is furnished with a transmitting and a receiving telephone and with a telephone-switch for connecting the telephones into a bridge of the line-circuit. The line-wires 3 and 4 are extended beroo yond the points of connection therewith of the telephones at station l) to bus-bars or points of distribution 7L and c'. In each of these extensions are distributed serially several impedance-coi1s7c,l, and 'm and 7c', Z', and 105 m', respectively. These coils should be of I gn 'comparatively low resistance, but of high impedance. Abridge 1l is taken from the conductor 3 between the coils la and Z to the corresponding point of conductor 4. Similarly a bridge l2 is formed between the conductors 3 and 4 from points intermediate of coils Z andfm and Z and m', respectively. These' bridges contain condensers o and p, which may be of about one microfarad capacity. The extension-lines to stations E and F are represented as being connected together in a continuous circuit of ordinary arrangement, the two sides of the circuit being connected with the two points of distribution h and t', respectively,through impedance-coils q and r. The central source a, produces current in both the lines l 2 and 3 4 to excite the transmitting-telephones at the stations of those lines when the telephones are in use, and inasmuch as these lines are united into a continuous circuit with respect to telephonie currents through the medium of the repeatingcoil b the users of the telephones at the two stations may converse with each other. Meantimecurrent is supplied also through the centers hito the extension-lines 5 6 and 7 8,whicl1 Y are united at the subcenter or branch station.

If impedance-coils alone be employed in the extensions of conductors 3 and 4 to the centers of current distribution of however great inductance, the telephonie currents produced in the circuits of the extension-lines find their way into the circuit 3 4, and thus interfere with transmission between the stations C and D, while likewise telephonie undulations in the latter circuits are propagated into the circuits of the extension-lines and interfere with conversation overthose lines.- It' the bridges l1 and 12,0r even one of them, be supplied with a resistance-coil in the bridge, as described in the patent before mentioned, the cross-talk or propagation of telephonie undulations from one of the independent circuits into the other is greatly reduced or may be completely prevented; but such a shunt involves a continuous waste of current, with reduction of the effective potential between the points of distribution if the line 3 4 be of considerable resistance. When the condensers are included in the bridges, such waste of current is of course avoided, while the organization is equally efficient in preventing the leakage of telephonie current from either circuit into the other. A single bridge, including the condenser, maybe employed with fairly good resuits; but for perfect suppression of crosstalk between circuits several such Vbridges should be employed.

The invention is defined in the following claims:

l. The combination with a circuit and means for producing varying currents and steady currents in said circuit, of a large imof the circuit distributed across the same at the point characterized by the aforesaid impedance, whereby the circuit is divided into two sections and varying currents produced in one section are prevented from passing to the other section, while the two sections are united to permit the passage of steady current from one section to the other, as described.

2. The combination with a circuit 3 4 and means for producing varying current therein, of a second circuit 5 6 connected with th'e first-mentioned circuit, a device in the lastmentioned circuit adapted to respond to the varying currents produced in the first cirl cuit, means for producing a flow of steady current between the two circuits, a number of impedance-coils distributed serially in the circuit of the steady current, and a bridge or bridges of the circuit including condensers at points between said im pedance-coils,whereby the vtwo circuits are rendered independent with respect to varying currents, while permitting the flow of steady current between them, substantially as set forth.

3. 'The combination with two tele phone-circuits connected in parallel with one another and telephonie apparatus in each circuit, of a source of steady current in .one of the circuits adapted to supply current to the other circuit, a number of impedancecoils serially connected in the circuit of said source of steady current between the two telephonecircuits, a bridge of the circuit between each two impedance-coils and a condenser in each bridge, whereby the two circuits are rendered 1 telephonically independent although one of them is receiving steady current from the other, substantially as set forth.

4L. In combination, two telephone-circuits, two conductors uniting the said two circuits, means for producing a flow of steady current between the two circuits, several impedancecoils in each of the conductors, bridges between said conductors intermediate of the repeating-coils, and condensers in the bridges, as described.

5. The combination with a main telephonecircuit uniting two stations with transmitting and receiving telephones in the circuits, a source of current in a bridge of the telephonecircnit, united extension telephone-lines each with transmitting and receiving telephones at its station, a branch from each side of said main telephone-circuit to a corresponding side of the extension-line circuit, several impedance-coils in the said branch or branches, and bridges of the circuits containing condensersintermediate of the impedance-coils; whereby all transmitting-telephones are simultaneously supplied with current while the independence of the telephone-circuits is preserved.

In witness whereof I hereunto subscribe my y name this 22d day ofDecember, A. D. 1899.

CHARLES E. SCRIBNER.

Witnesses:

ELLA EDLER, FLORENCE E. Sutri/inns. 

